From cb9444130662c6c13022579c861098f212db2562 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Thu, 25 Mar 2021 11:08:13 -0700
Subject: [PATCH] sysctl: add proc_dou8vec_minmax()

Networking has many sysctls that could fit in one u8.

This patch adds proc_dou8vec_minmax() for this purpose.

Note that the .extra1 and .extra2 fields are pointing
to integers, because it makes conversions easier.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 fs/proc/proc_sysctl.c  |  6 ++++
 include/linux/sysctl.h |  2 ++
 kernel/sysctl.c        | 65 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 73 insertions(+)

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 984e42f8cb11..7256b8962e3c 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -1108,6 +1108,11 @@ static int sysctl_check_table_array(const char *path, struct ctl_table *table)
 			err |= sysctl_err(path, table, "array not allowed");
 	}
 
+	if (table->proc_handler == proc_dou8vec_minmax) {
+		if (table->maxlen != sizeof(u8))
+			err |= sysctl_err(path, table, "array not allowed");
+	}
+
 	return err;
 }
 
@@ -1123,6 +1128,7 @@ static int sysctl_check_table(const char *path, struct ctl_table *table)
 		    (table->proc_handler == proc_douintvec) ||
 		    (table->proc_handler == proc_douintvec_minmax) ||
 		    (table->proc_handler == proc_dointvec_minmax) ||
+		    (table->proc_handler == proc_dou8vec_minmax) ||
 		    (table->proc_handler == proc_dointvec_jiffies) ||
 		    (table->proc_handler == proc_dointvec_userhz_jiffies) ||
 		    (table->proc_handler == proc_dointvec_ms_jiffies) ||
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 51298a4f4623..d99ca99837de 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -53,6 +53,8 @@ int proc_douintvec(struct ctl_table *, int, void *, size_t *, loff_t *);
 int proc_dointvec_minmax(struct ctl_table *, int, void *, size_t *, loff_t *);
 int proc_douintvec_minmax(struct ctl_table *table, int write, void *buffer,
 		size_t *lenp, loff_t *ppos);
+int proc_dou8vec_minmax(struct ctl_table *table, int write, void *buffer,
+			size_t *lenp, loff_t *ppos);
 int proc_dointvec_jiffies(struct ctl_table *, int, void *, size_t *, loff_t *);
 int proc_dointvec_userhz_jiffies(struct ctl_table *, int, void *, size_t *,
 		loff_t *);
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 62fbd09b5dc1..90d2892ef6a3 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1034,6 +1034,65 @@ int proc_douintvec_minmax(struct ctl_table *table, int write,
 				 do_proc_douintvec_minmax_conv, &param);
 }
 
+/**
+ * proc_dou8vec_minmax - read a vector of unsigned chars with min/max values
+ * @table: the sysctl table
+ * @write: %TRUE if this is a write to the sysctl file
+ * @buffer: the user buffer
+ * @lenp: the size of the user buffer
+ * @ppos: file position
+ *
+ * Reads/writes up to table->maxlen/sizeof(u8) unsigned chars
+ * values from/to the user buffer, treated as an ASCII string. Negative
+ * strings are not allowed.
+ *
+ * This routine will ensure the values are within the range specified by
+ * table->extra1 (min) and table->extra2 (max).
+ *
+ * Returns 0 on success or an error on write when the range check fails.
+ */
+int proc_dou8vec_minmax(struct ctl_table *table, int write,
+			void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct ctl_table tmp;
+	unsigned int min = 0, max = 255U, val;
+	u8 *data = table->data;
+	struct do_proc_douintvec_minmax_conv_param param = {
+		.min = &min,
+		.max = &max,
+	};
+	int res;
+
+	/* Do not support arrays yet. */
+	if (table->maxlen != sizeof(u8))
+		return -EINVAL;
+
+	if (table->extra1) {
+		min = *(unsigned int *) table->extra1;
+		if (min > 255U)
+			return -EINVAL;
+	}
+	if (table->extra2) {
+		max = *(unsigned int *) table->extra2;
+		if (max > 255U)
+			return -EINVAL;
+	}
+
+	tmp = *table;
+
+	tmp.maxlen = sizeof(val);
+	tmp.data = &val;
+	val = *data;
+	res = do_proc_douintvec(&tmp, write, buffer, lenp, ppos,
+				do_proc_douintvec_minmax_conv, &param);
+	if (res)
+		return res;
+	if (write)
+		*data = val;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(proc_dou8vec_minmax);
+
 static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
 					unsigned int *valp,
 					int write, void *data)
@@ -1582,6 +1641,12 @@ int proc_douintvec_minmax(struct ctl_table *table, int write,
 	return -ENOSYS;
 }
 
+int proc_dou8vec_minmax(struct ctl_table *table, int write,
+			void *buffer, size_t *lenp, loff_t *ppos)
+{
+	return -ENOSYS;
+}
+
 int proc_dointvec_jiffies(struct ctl_table *table, int write,
 		    void *buffer, size_t *lenp, loff_t *ppos)
 {
-- 
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